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* Room S-111
Friday, September 25, 2009, 1:00 PM
Dr. Spiro Alexandratosp
Hunter College
The Earth in Crisis: Pollution of Water in the Biosphere – Current Status and Steps Towards Renewal
Groundwater is an essential resource yet it is being contaminated with metals and molecules that are highly toxic to plant and animal life. Metals (nickel, cobalt, chromium, copper, lead, cadmium, etc.) may be present at a level of 1 part per million – a level that seems low but is high enough to be toxic. As one of many examples, a site in the state of North Carolina, declared toxic by the US Environmental Protection Agency, is the former location of a battery recycling operation where lead from 95000 cubic meters of contaminated soil has migrated into the aquifer to a depth of 18 meters and now contaminates 320000 cubic meters of groundwater. Compounds that can contaminate groundwater include fuel components, pesticides, and steroids; this is especially serious because some alter the reproductive and endocrine systems of wildlife and humans by acting with estrogen, androgen, and thyroid hormone receptors. Current approaches to the removal of toxic metals from groundwater will be described, including contributions from our laboratory that have led to the development of three polymer-supported reagents: one for the removal of arsenic, one for the removal of radioactive metals, and one for the removal of perchlorate.
Friday, October 16, 2009, 1:00 PM
Dr. Gloria Proni
John Jay College of Criminal Justice
1. Probing Chirality of Diamines by CD-sensitive Dimeric Zn-porphyrin Tweezers
For more than a decade, dimeric metalloporphyrin hosts, known as tweezers, have been successfully applied as chirality probes for determination of absolute configuration of a wide variety of chiral synthetic compounds and natural products. The tweezer methodology relies on a stereo-differentiating host/guest complexation between bis-porphyrin tweezer and chiral substrate containing two sites of coordination. This results in an intense exciton-split CD signal, which is diagnostic for the absolute configuration of the guest. In this presentation recent advances in the technique will be discussed, in particular its application to several classes of substrates and important natural compounds.
2. Index of Freshness Analysis of Tuna Sushi and Sashimi Gathered from New York City Markets
News articles have shown that the quality and safety of raw fish sold in New York City is questionable. Because of the potential dangers associated with the consumption of raw fish, the freshness of the raw tuna in the form of sushi and sashimi from 12 restaurants in New York metropolitan area was investigated. The determination of the index of freshness (K coefficient) and consequently the biochemical age of several fish samples was achieved by using a technique that extracts and quantifies the products of the ATP breakdown during fish aging. In this presentation data regarding the biochemical ages of the samples and their index of freshness are presented.
Friday, November 20, 2009, 1:00 PM
Dr. Mihaela Bojin
Queensborough Community College, CUNY
What Happens To Amino Acids When the pH Changes?
Using computational chemistry we explore different conformations of a series of amino acids using density functional (DFT) methods. Amino acids intra- and intermolecular interactions are significantly influenced by surrounding residues and the pH of their environments. Hydrogen bonds, in particular, control folding in secondary and tertiary structures in proteins and significantly affect enzymatic activity. By employing the B3LYP/6-31+G(d,p) method we determine the major conformers of aspartic acid (Asp), asparagine (Asn), serine (Ser) and threonine (Thr) in their neutral (no charges), zwitterionic, acidic (protonated), and basic (deprotonated) forms, in gaseous and aqueous media. We find that changes in acidity critically influence and limit hydrogen bonding patterns, and thus the stability of the resulting conformers.
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